/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License.  You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.catalina.filters;

import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import java.io.IOException;

/**
 * <p>Example filter that sets the character encoding to be used in parsing the
 * incoming request, either unconditionally or only if the client did not
 * specify a character encoding.  Configuration of this filter is based on
 * the following initialization parameters:</p>
 * <ul>
 * <li><strong>encoding</strong> - The character encoding to be configured
 * for this request, either conditionally or unconditionally based on
 * the <code>ignore</code> initialization parameter.  This parameter
 * is required, so there is no default.</li>
 * <li><strong>ignore</strong> - If set to "true", any character encoding
 * specified by the client is ignored, and the value returned by the
 * <code>selectEncoding()</code> method is set.  If set to "false,
 * <code>selectEncoding()</code> is called <strong>only</strong> if the
 * client has not already specified an encoding.  By default, this
 * parameter is set to "false".</li>
 * </ul>
 * <p>
 * <p>Although this filter can be used unchanged, it is also easy to
 * subclass it and make the <code>selectEncoding()</code> method more
 * intelligent about what encoding to choose, based on characteristics of
 * the incoming request (such as the values of the <code>Accept-Language</code>
 * and <code>User-Agent</code> headers, or a value stashed in the current
 * user's session.</p>
 */
public class SetCharacterEncodingFilter extends FilterBase {

	private static final Log log =
			LogFactory.getLog(SetCharacterEncodingFilter.class);


	// ----------------------------------------------------- Instance Variables

	/**
	 * The default character encoding to set for requests that pass through
	 * this filter.
	 */
	private String encoding = null;
	/**
	 * Should a character encoding specified by the client be ignored?
	 */
	private boolean ignore = false;

	public String getEncoding() {
		return encoding;
	}

	public void setEncoding(String encoding) {
		this.encoding = encoding;
	}

	public boolean isIgnore() {
		return ignore;
	}

	public void setIgnore(boolean ignore) {
		this.ignore = ignore;
	}


	// --------------------------------------------------------- Public Methods

	/**
	 * Select and set (if specified) the character encoding to be used to
	 * interpret request parameters for this request.
	 *
	 * @param request  The servlet request we are processing
	 * @param response The servlet response we are creating
	 * @param chain    The filter chain we are processing
	 * @throws IOException      if an input/output error occurs
	 * @throws ServletException if a servlet error occurs
	 */
	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
	                     FilterChain chain)
			throws IOException, ServletException {

		// Conditionally select and set the character encoding to be used
		if (ignore || (request.getCharacterEncoding() == null)) {
			String characterEncoding = selectEncoding(request);
			if (characterEncoding != null) {
				request.setCharacterEncoding(characterEncoding);
			}
		}

		// Pass control on to the next filter
		chain.doFilter(request, response);
	}


	// ------------------------------------------------------ Protected Methods

	@Override
	protected Log getLogger() {
		return log;
	}

	/**
	 * Select an appropriate character encoding to be used, based on the
	 * characteristics of the current request and/or filter initialization
	 * parameters.  If no character encoding should be set, return
	 * <code>null</code>.
	 * <p>
	 * The default implementation unconditionally returns the value configured
	 * by the <strong>encoding</strong> initialization parameter for this
	 * filter.
	 *
	 * @param request The servlet request we are processing
	 */
	protected String selectEncoding(ServletRequest request) {
		return this.encoding;
	}
}
